Reflection

Reflection of Waves

Definition of Reflection

• Reflection is the process in which a wave encounters a surface and bounces back.
• The incident wave that approaches the surface is known as the incident wave.
• The wave that returns back after hitting the surface is known as the reflected wave.

Law of Reflection

• The law of reflection states that the angle of incidence is equal to the angle of reflection, measured from the normal.
• The normal is an imaginary line at right angles (perpendicular) to the surface at the point of incidence.
• The wave incident angle and reflected wave angle are always measured relative to the normal, not the surface.

Behaviour of Reflection

• Reflection can occur on all types of waves including sound waves, light waves and water waves.
• Smooth surfaces such as mirrors produce clear reflections (known as specular reflection) because the light rays are reflected in the same direction.
• Rough surfaces such as white paper scatter light rays in various directions (this is known as diffuse reflection). This is why we can see non-shiny objects from all angles.

Applications of Reflection

• Reflection has numerous applications in our everyday life like mirrors, periscopes, reflective clothing, and more.
• In technology, it is used in devices such as radar and sonar which uses the reflection of radio and sound waves respectively to detect objects.
• The phenomenon of echo is also an example of wave reflection.

Key Points in Reflection

• For a wave reflection to occur, the surface it encounters should be large compared to the wavelength of the incident wave.
• Factors such as the textural properties of the reflecting surface, the angle of incidence and the wavelength of the wave determine the behaviour of the reflected wave.